Neural crest lineage in the protovertebrate model Ciona.

Abstract

Neural crest cells are multipotent progenitors that produce defining features of vertebrates such as the 'new head'¹. Here we use the tunicate, Ciona, to explore the evolutionary origins of neural crest since this invertebrate chordate is among the closest living relatives of vertebrates^2-4. Previous studies identified two potential neural crest cell types in Ciona, sensory pigment cells and bipolar tail neurons^5,6. Recent findings suggest that  bipolar tail neurons are homologous to cranial sensory ganglia rather than derivatives of neural crest^7,8. Here we show that the pigment cell lineage also produces neural progenitor cells that form regions of the juvenile nervous system following metamorphosis. Neural progenitors are also a major derivative of neural crest in vertebrates, suggesting that the last common ancestor of tunicates and vertebrates contained a multipotent progenitor population at the neural plate border. It would therefore appear that a key property of neural crest, multipotentiality, preceded the emergence of vertebrates.